Bottom Line:
However, the few empirical attempts to test this hypothesis do not use natural groups and conflate measures of in-group and unbiased cooperative behaviour.Conflict was associated with reduced donations to out-group schools and the return of out-group letters, but we found no evidence that it influences in-group cooperation.Rather, socio-economic status was the major determinant of cooperative behaviour.

Affiliation: Department of Anthropology, University College London, London WC1H 0BW, UK antonio.silva.09@ucl.ac.uk.

ABSTRACTThe idea that cohesive groups, in which individuals help each other, have a competitive advantage over groups composed of selfish individuals has been widely suggested as an explanation for the evolution of cooperation in humans. Recent theoretical models propose the coevolution of parochial altruism and intergroup conflict, when in-group altruism and out-group hostility contribute to the group's success in these conflicts. However, the few empirical attempts to test this hypothesis do not use natural groups and conflate measures of in-group and unbiased cooperative behaviour. We conducted field experiments based on naturalistic measures of cooperation (school/charity donations and lost letters' returns) with two religious groups with an on-going history of conflict-Catholics and Protestants in Northern Ireland. Conflict was associated with reduced donations to out-group schools and the return of out-group letters, but we found no evidence that it influences in-group cooperation. Rather, socio-economic status was the major determinant of cooperative behaviour. Our study presents a challenge to dominant perspectives on the origins of human cooperation, and has implications for initiatives aiming to promote conflict resolution and social cohesion.

RSPB20141435F3: Letters returned by neighbourhood threat index. Predicted probability of return of in-group, out-group and neutral lost letters by the level of neighbourhood threat index. This measure is the neighbourhood aggregate of the continuous factors, which are composed of the variables related to the individual exposure to sectarian attacks and threat (details are provided in the electronic supplementary material). This effect is controlled for neighbourhood religious composition, income deprivation, number of post-boxes, population density and level of religious heterogeneity. Error bars represent the standard errors. (Online version in colour.)

Mentions:
We also found that intergroup conflict was associated with reduced levels of out-group cooperation; individuals who had experienced greater sectarian violence and felt the most threatened by the other group were less likely to donate money to an out-group school (table 2), and in neighbourhoods with higher mean threat levels a lost letter addressed to an out-group institution (relative to the majority population) was less likely to be returned (table 3). At the mean values for all other traits, individuals with the lowest threat levels had a 64% chance of donating to an out-group school, compared with 20% chance for individuals with the highest threat levels (figure 2). For lost letters there was a 70% chance of out-group letters being returned in low threat neighbourhoods, compared with only 30% in high threat neighbourhoods (figure 3). However, we found no evidence for an association between intergroup conflict and cooperation with the in-group, with neither individual nor neighbourhood threat levels significantly predicting donations to in-group schools or returns of in-group letters, respectively (tables 2 and 3; figures 2 and 3). We also did not find any evidence that proximity between groups—measured by the levels of religious heterogeneity in a neighbourhood—predicts any type of cooperative behaviour in either donations or lost letters (tables 2 and 3).Table 2.

RSPB20141435F3: Letters returned by neighbourhood threat index. Predicted probability of return of in-group, out-group and neutral lost letters by the level of neighbourhood threat index. This measure is the neighbourhood aggregate of the continuous factors, which are composed of the variables related to the individual exposure to sectarian attacks and threat (details are provided in the electronic supplementary material). This effect is controlled for neighbourhood religious composition, income deprivation, number of post-boxes, population density and level of religious heterogeneity. Error bars represent the standard errors. (Online version in colour.)

Mentions:
We also found that intergroup conflict was associated with reduced levels of out-group cooperation; individuals who had experienced greater sectarian violence and felt the most threatened by the other group were less likely to donate money to an out-group school (table 2), and in neighbourhoods with higher mean threat levels a lost letter addressed to an out-group institution (relative to the majority population) was less likely to be returned (table 3). At the mean values for all other traits, individuals with the lowest threat levels had a 64% chance of donating to an out-group school, compared with 20% chance for individuals with the highest threat levels (figure 2). For lost letters there was a 70% chance of out-group letters being returned in low threat neighbourhoods, compared with only 30% in high threat neighbourhoods (figure 3). However, we found no evidence for an association between intergroup conflict and cooperation with the in-group, with neither individual nor neighbourhood threat levels significantly predicting donations to in-group schools or returns of in-group letters, respectively (tables 2 and 3; figures 2 and 3). We also did not find any evidence that proximity between groups—measured by the levels of religious heterogeneity in a neighbourhood—predicts any type of cooperative behaviour in either donations or lost letters (tables 2 and 3).Table 2.

Bottom Line:
However, the few empirical attempts to test this hypothesis do not use natural groups and conflate measures of in-group and unbiased cooperative behaviour.Conflict was associated with reduced donations to out-group schools and the return of out-group letters, but we found no evidence that it influences in-group cooperation.Rather, socio-economic status was the major determinant of cooperative behaviour.

Affiliation:
Department of Anthropology, University College London, London WC1H 0BW, UK antonio.silva.09@ucl.ac.uk.

ABSTRACTThe idea that cohesive groups, in which individuals help each other, have a competitive advantage over groups composed of selfish individuals has been widely suggested as an explanation for the evolution of cooperation in humans. Recent theoretical models propose the coevolution of parochial altruism and intergroup conflict, when in-group altruism and out-group hostility contribute to the group's success in these conflicts. However, the few empirical attempts to test this hypothesis do not use natural groups and conflate measures of in-group and unbiased cooperative behaviour. We conducted field experiments based on naturalistic measures of cooperation (school/charity donations and lost letters' returns) with two religious groups with an on-going history of conflict-Catholics and Protestants in Northern Ireland. Conflict was associated with reduced donations to out-group schools and the return of out-group letters, but we found no evidence that it influences in-group cooperation. Rather, socio-economic status was the major determinant of cooperative behaviour. Our study presents a challenge to dominant perspectives on the origins of human cooperation, and has implications for initiatives aiming to promote conflict resolution and social cohesion.